`@JsonSetter(nulls = Nulls.SKIP)` doesn't work in some situations

[Asapin]

Search before asking

• I searched in the issues and found nothing similar.

Describe the bug

We're using @JsonSetter(nulls = Nulls.SKIP) quite heavily in our code base to avoid dealing with null values, but yesterday I noticed that some fields contain null despite being annotated with @JsonSetter(nulls = Nulls.SKIP)

Version Information

2.15.3, 2.15.4, 2.16.0, 2.16.1, 2.16.2, 2.17.0

Reproduction

public class Main {
    static class Outer {
        @JsonSetter(nulls = Nulls.SKIP)
        private final List<Middle> list1 = new ArrayList<>();

        public Outer() {
        }

        public List<Middle> getList1() {
            return list1;
        }
    }

    static class Middle {
        @JsonSetter(nulls = Nulls.SKIP)
        private final List<Inner> list1 = new ArrayList<>();
        private final String field1;

        @ConstructorProperties({"field1"})
        public Middle(String field1) {
            this.field1 = field1;
        }

        public List<Inner> getList1() {
            return list1;
        }

        public String getField1() {
            return field1;
        }
    }

    static class Inner {
        private final String field1;

        @ConstructorProperties({"field1"})
        public Inner(String field1) {
            this.field1 = field1;
        }

        public String getField1() {
            return field1;
        }
    }

    public static void main(String[] args) {
        String json = """
                {
                    "list1": [
                        {
                            "list1": null,
                            "field1": "data"
                        }
                    ]
                }
                """;
        ObjectMapper objectMapper = new ObjectMapper();
        Outer outer;
        try {
            outer = objectMapper.readValue(json, Outer.class);
        } catch (JsonProcessingException e) {
            throw new RuntimeException(e);
        }
        validateNotNull(outer);
        validateNotNull(outer.getList1());
        for (Middle middle : outer.getList1()) {
            validateNotNull(middle);
            validateNotNull(middle.getField1());
            validateNotNull(middle.getList1());
        }
    }

    private static void validateNotNull(Object o) {
        if (o == null) {
            throw new IllegalStateException("Shouldn't be null");
        }
    }
}

Expected behavior

middle.getList1() shouldn't be null since it's annotated with @JsonSetter(nulls = Nulls.SKIP)

Additional context

Any of the following seems to fix the issue, but is not really feasible to do:

• Change the order of fields in the JSON:

{
    "list1": [
        {
            "field1": "data",
            "list1": null
        }
    ]
}

• Remove final from Middle#field1 and remove this field from constructor parameters

[JooHyukKim]

Sorry late asking, but are the versions in "Version Informations" all that are not working?

[Asapin]

Yes, these are versions where the bug happens (didn't test older versions though).

I first discovered this issue when using 2.15.3. Later I tried newer versions hoping that this was fixed, but the issue was still reproducible with all newer versions as well.

[JooHyukKim]

Sorry late again @Asapin, one more question is which latest version did it work? 2.15.2? 👈🏼 Finding this out would help alot.

I modified a bit around visibility of fields (and simplified a bit), it seems to work. If urgent, I guess possible work around would be modifying visilbity via mapper.setVisibility()? Maybe others will know more.

public class BeanDeserializerModifier4216Test {
    static class Outer {
        @JsonSetter(nulls = Nulls.SKIP)
        public List<Middle> list1 = new ArrayList<>();
    }

    static class Middle {
        @JsonSetter(nulls = Nulls.SKIP)
        public List<Inner> list1 = new ArrayList<>();
        public String field1;
    }

    static class Inner {
        private final String field1;

        @ConstructorProperties({"field1"})
        public Inner(String field1) {
            this.field1 = field1;
        }

        public String getField1() {
            return field1;
        }
    }

    public static void main(String[] args) {
        try {
            Outer outer = new ObjectMapper().readValue("""
                    {
                        "list1": [
                            {
                                "list1": null,
                                "field1": "data"
                            }
                        ]
                    }""", Outer.class);
            validateNotNull(outer);
            validateNotNull(outer.list1);
            for (Middle middle : outer.list1) {
                validateNotNull(middle);
                validateNotNull(middle.field1);
                validateNotNull(middle.list1);
            }
        } catch (JsonProcessingException e) {
            throw new RuntimeException(e);
        }
    }

    private static void validateNotNull(Object o) {
        if (o == null) {
            throw new IllegalStateException("Shouldn't be null");
        }
    }
}

[Asapin]

@JooHyukKim
I don't think it ever worked before. I tried the following versions: 2.15.2, 2.15.1, 2.15.0, 2.14.0, 2.13.0, 2.12.0, 2.11.0, 2.10.0 and 2.9.0, and the all failed this test, but they all work if I change the order of fields in the JSON

[JooHyukKim]

Strange... seems like bug. If you can either...

• change the order of fields in the JSON
• or change modifier as I suggested above

as a temporary work-around, that'd be great 👍🏼

[cowtowncoder]

Changing order might suggest the issue has something to do with buffering (as buffering only needed in some cases depending on input order of content).

[cowtowncoder]

Ahhh. Actually, it is sort of due to buffering... but quite indirectly. @JooHyukKim figured it out; it's missing logic from set() methods of FieldProperty and MethodProperty.